179 lines
5.2 KiB
C
179 lines
5.2 KiB
C
/*
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* advertising materials, and other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/*
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FUNCTION
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<<fopen>>---open a file
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INDEX
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fopen
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INDEX
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_fopen_r
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ANSI_SYNOPSIS
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#include <stdio.h>
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FILE *fopen(const char *<[file]>, const char *<[mode]>);
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FILE *_fopen_r(void *<[reent]>,
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const char *<[file]>, const char *<[mode]>);
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TRAD_SYNOPSIS
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#include <stdio.h>
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FILE *fopen(<[file]>, <[mode]>)
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char *<[file]>;
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char *<[mode]>;
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FILE *_fopen_r(<[reent]>, <[file]>, <[mode]>)
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char *<[reent]>;
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char *<[file]>;
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char *<[mode]>;
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DESCRIPTION
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<<fopen>> initializes the data structures needed to read or write a
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file. Specify the file's name as the string at <[file]>, and the kind
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of access you need to the file with the string at <[mode]>.
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The alternate function <<_fopen_r>> is a reentrant version.
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The extra argument <[reent]> is a pointer to a reentrancy structure.
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Three fundamental kinds of access are available: read, write, and append.
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<<*<[mode]>>> must begin with one of the three characters `<<r>>',
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`<<w>>', or `<<a>>', to select one of these:
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o+
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o r
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Open the file for reading; the operation will fail if the file does
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not exist, or if the host system does not permit you to read it.
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o w
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Open the file for writing @emph{from the beginning} of the file:
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effectively, this always creates a new file. If the file whose name you
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specified already existed, its old contents are discarded.
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o a
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Open the file for appending data, that is writing from the end of
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file. When you open a file this way, all data always goes to the
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current end of file; you cannot change this using <<fseek>>.
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o-
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Some host systems distinguish between ``binary'' and ``text'' files.
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Such systems may perform data transformations on data written to, or
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read from, files opened as ``text''.
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If your system is one of these, then you can append a `<<b>>' to any
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of the three modes above, to specify that you are opening the file as
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a binary file (the default is to open the file as a text file).
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`<<rb>>', then, means ``read binary''; `<<wb>>', ``write binary''; and
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`<<ab>>', ``append binary''.
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To make C programs more portable, the `<<b>>' is accepted on all
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systems, whether or not it makes a difference.
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Finally, you might need to both read and write from the same file.
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You can also append a `<<+>>' to any of the three modes, to permit
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this. (If you want to append both `<<b>>' and `<<+>>', you can do it
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in either order: for example, <<"rb+">> means the same thing as
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<<"r+b">> when used as a mode string.)
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Use <<"r+">> (or <<"rb+">>) to permit reading and writing anywhere in
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an existing file, without discarding any data; <<"w+">> (or <<"wb+">>)
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to create a new file (or begin by discarding all data from an old one)
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that permits reading and writing anywhere in it; and <<"a+">> (or
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<<"ab+">>) to permit reading anywhere in an existing file, but writing
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only at the end.
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RETURNS
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<<fopen>> returns a file pointer which you can use for other file
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operations, unless the file you requested could not be opened; in that
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situation, the result is <<NULL>>. If the reason for failure was an
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invalid string at <[mode]>, <<errno>> is set to <<EINVAL>>.
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PORTABILITY
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<<fopen>> is required by ANSI C.
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Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
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<<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "%W% (Berkeley) %G%";
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#endif /* LIBC_SCCS and not lint */
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#include <stdio.h>
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#include <errno.h>
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#include "local.h"
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#ifdef __CYGWIN__
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#include <fcntl.h>
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#endif
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#include <sys/lock.h>
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FILE *
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_DEFUN (_fopen_r, (ptr, file, mode),
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struct _reent *ptr _AND
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_CONST char *file _AND
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_CONST char *mode)
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{
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register FILE *fp;
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register int f;
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int flags, oflags;
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if ((flags = __sflags (ptr, mode, &oflags)) == 0)
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return NULL;
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if ((fp = __sfp (ptr)) == NULL)
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return NULL;
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if ((f = _open_r (ptr, file, oflags, 0666)) < 0)
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{
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fp->_flags = 0; /* release */
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return NULL;
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}
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fp->_file = f;
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fp->_flags = flags;
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fp->_cookie = (_PTR) fp;
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fp->_read = __sread;
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fp->_write = __swrite;
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fp->_seek = __sseek;
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fp->_close = __sclose;
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if (fp->_flags & __SAPP)
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_fseek_r (ptr, fp, 0, SEEK_END);
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#ifdef __SCLE
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if (__stextmode (fp->_file))
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fp->_flags |= __SCLE;
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#endif
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#ifndef __SINGLE_THREAD__
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__lock_init_recursive (*(_LOCK_RECURSIVE_T *)&fp->_lock);
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#endif
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return fp;
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}
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#ifndef _REENT_ONLY
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FILE *
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_DEFUN (fopen, (file, mode),
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_CONST char *file _AND
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_CONST char *mode)
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{
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return _fopen_r (_REENT, file, mode);
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}
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#endif
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